This invention is directed to imaging devices that use a lens in combination with a sensor. The sensor is moved utilizing X-Y linear translational motion through the imaging area of the lens.
Various imaging systems are known for scanning fields of view and fields of regard. A particularly useful imaging system is one that scans then locks on targets in various weapon delivery systems and/or guided projectiles. Such imaging systems generally scan in either the visible or the infrared spectral region. Useful as sensors or pick up devices in these systems are television tubes and linear or matrix array devices such as charge coupled devices and infrared detectors including infrared focal plane arrays.
Since infrared focal plane arrays or charge coupled TV camera imaging devices typically have very limited fields of view it is necessary to mount such devices on housings which are movable in order to utilize such devices in scanning, searching or target tracking over a larger viewing area, called the field of regard. One method to increase the field of regard of these devices is to mount both the device and any associated optics for conveying images to the device in a gimbal mount. One such gimbal mount is shown and described in U.S. Pat. No. 4,024,392, entitled Gimballed Active Optical System. This patent describes a device which includes a refractor having a sensor fixedly mounted to the refractor the totality of which is suspended in a two axis gimbal. Movement about the two axes of the gimbal allows for scanning and other dynamic motions necessary to increase the field of regard of the device. U.S. Pat. No. 4,034,208, entitled Acceleration Aided Tracking Of A Designated Target, provides for computer aided tracking utilizing a gimballed sensor device. In this device a three action gimbal motion is described allowing for rotation of the sensor about roll, azimuth and elevational axes.
Because the optics and the sensor all must be gimballed together to move as a unit, the gimbal devices described above are inherently complex. If cryogenic cooling is necessary for the operation of infrared devices, this adds additional components that must be incorporated on the gimbal mount and moved for scanning, tracking or the like. In order to simplify such devices U.S. Pat. No. 4,886,330 describes an infrared imaging system that utilizes a mirror that is rotated for tracking the target about the azimuth axis and is tilted for tracking the target about the elevational axis. An inherent problem with this design is that the image will flip as the mirror is rotated in azimuth.
For both azimuth-elevational moved mirrors and gimbal mounted devices, a protective dome is needed to shield the components from the air stream they move through. Since such domes must not distort the optics of the system, the domes must themselves be of optical quality. Further, especially in a gimbal mounted system, the dome must be sufficiently large to cover the totality of the movement of the gimbal. This requires the dome to be spherical, parabolic or of other exotic shape. Inherently, such domes are expensive components. Additionally, inherently such domes do not lead to "low observability" or stealth characteristics. Furthermore, the imaging optics must be custom designed to correct for the refractive power of these domes.